1. Field of the Invention
The present invention relates generally to a lumber making attachment of use with chain saws, and more particularly, to an improved saw guide which may be attached to a portable chain saw for the purpose of sawing lumber from logs and the like.
2. Description of the Prior Art
Saw guides for use with portable chain saws are well known in the lumber industry. Such guides are typically used for ripping and cross-cutting operations such as the squaring of the ends and sides of logs and the trimming off of the sides of boards and other types of lumber.
For example, the saw guide disclosed in U.S. Pat. No. 3,051,203 to Hayden accomplishes such operation through the utilization of various roller combinations to both support the saw guide and attached chain saw and allow its free movement along a guide member attached to a flat upper surface of the lumber being cut. The flat upper surface is supplied by either sawing the upper surface of the log itself or by attaching a flat board thereto. The guide member, which may be a pipe or similar straight channel, is attached to the flat surface in a manner so as to continuously cooperate with vertically disposed rollers provided in the saw guide carriage along the length of the log during the sawing operation, thereby enabling the operator to make straight and substantially flat cuts along the entire length of the log.
It has been found that saw guides of this type have great practical value in that they allow the use of chain saws and other portable power driven saws for cutting boards and similar lumber products from logs directly in the forest or farmyard, thereby avoiding the necessity and expense of hauling the logs to a saw mill.
However, certain problems have been encountered in using conventional saw guides such as that disclosed in the above-discussed Hayden patent. One of these problems has arisen due to the fact that sawdust and wood chips frequently become lodged in the guide carriage and its associated roller during the sawing operation. Whenever this condition occurs, it results in an interference with the free movement of the guide carriage along the guide member. This is due to the fact that the sawdust prevents the guide carriage rollers from freely turning against the guide member and flat upper surface of the log, thereby jamming the saw guide in place at that point or otherwise causing uneven cuts of the lumber. In order to free the saw guide, the operator must back the guide carriage along the guide member and clear the roller path or, in some cases, must actually remove the guide carriage and attached chain saw from the guide member. Of course, the necessity of clearing sawdust and wood chips from the saw guide from time to time is highly undesirable in that it substantially decreases the output and efficiency of the operator during the sawing process. In addition, the natural tendency of the rollers to ride up over sawdust and wood chip deposits in their path often results in uneven cuts along the cutting surface.
Another drawback experienced with the Hayden saw guide is that it is designed so that the operator must be positioned immediately above the saw in order to push the device along the cutting surface, thereby causing sawdust to be thrown directly up into the operator's face and, hence, interfering with his vision and normal breathing.
Furthermore, the means for securing the frame of the Hayden saw guide to the chain saw requires that holes be drilled in the saw bar of the chain saw at specific points so that in operation the cutting elements of the chain saw will engage the lumber being cut at a predetermined angle which is correlated to the hardness and texture of that particular lumber. Therefore, if it is later desired to cut lumber having a substantially different hardness and texture, the chain saw must be removed from the saw guide and new holes must be drilled in the saw bar in order to allow for a different cutting angle.
An additional problem found with conventional saw guides is that in many cases uniform parallel cuts at the outer edge of a log cannot be made due to the fact that it is impossible to rigidly attach and maintain the flat board along which the saw guide travels to the curved upper surface of the log near its edge with the flat top surface of the board perpendicular to the desired saw cut.